1. Field of the Invention
The present invention relates to a linear drive ultrasonic motor.
2. Description of the Related Art
A vibration apparatus in Japanese Patent No. 3524248 Specification (FIGS. 3A and 3B) can be cited as an example of a conventional linear drive ultrasonic motor. Here, FIG. 3A and FIG. 3B are diagrams showing a structure of the conventional linear drive ultrasonic motor, where FIG. 3A is an exploded perspective view and FIG. 3B is a vertical cross-sectional view.
The vibration apparatus shown in FIG. 3A and FIG. 3B includes a case 906 which accommodates a vibrating body 901, a mobile object 904 which passes through the case 906 and makes a contact with the vibrating body 901, and a pressing spring 905 which generates pressing force (a bias) which brings the mobile object 904 and the vibrating body 901 in a pressurized contact. The pressing spring 905 is installed at an outer side of the case 906. An opening portion is formed in a side of the case 906, facing the vibrating body 901, and the pressing force of the pressing spring 905 acts on the vibrating body 901 through the opening portion. In other words, this vibration apparatus has a structure in which the pressing spring 905 is installed on the outer side of the case 906 while covering the opening portion of the case 906, and a deformed portion (a plane surface portion covering the opening portion) of the pressing spring 905 which generates the pressing force is exposed.
However, in the vibration apparatus described in Japanese Patent No. 3524248 Specification, when installed on some external apparatus, for avoiding a change in the pressing force of the pressing spring 905, there is a limitation of designing that the pressing spring 905 does not make a contact with a member of the external apparatus, in other words, that an arrangement is to be made to avoid the pressing spring 905.